Machine and method of expanding tube sections



April 21, 1970 w. A COLLINS MACHINE AND METHOD'OF EXPANDING TUBE SECTIONS 3 Sheets-Sheet 1 Filed Jan. 15, 1968 INVENTOR. I M47112 *2. I away;

April 21,1970 W.A.' COLLIINS I 6 MACHINEANDMETHOD OF EXPANDING TUBE SECTIONS Filed Jan. 15, 1968 1 r v I 3 Sheejizlsz-Sheeo 2 INVENTOR. I

A ril 21, 1970 w. A. COLLINS 0 MACHINE AND METHOD OF EXPANDING TUBE SECTIONS v I 3 Sheets-Sheet 8 Filed Jan. 15, 1968 MA 2 w m7. wx WQ 0 WWWW W United States Patent US. Cl. 29-1573 11 Claims ABSTRACT OF. THE DISCLOSURE The machine and method of the present application pertains to the threading of a continuous tube of conducting material back and forth through a stack of fins having a plurality of apertures which are in aligned relation to form a plurality of through openings. Within the tube is a wire having an expanding element on the trailing end which before the first and after each loop is formed is pulled a distance to draw the element through the straight portion located Within an opening to conductively and fixedly engage the tube wall with the fins. The element is pulled a sufficient distance beyond the straight portion to be located within the tube at a point where the next straight portion begins after the loop is formed. The extending length of wire is cut off leaving and end extending from the tube of a length to be secured by pulling jaws.

CROSS REFERENCE TO RELATED APPLICATIONS Reference may be had to applicants two copending applications, Ser. No. 693,355, filed Dec. 26, 1967, now Patent No. 3,440,704, for Method of Constructing a Continuous Tube Finned Heat Exchanger and Ser. No. 693,354, filed Dec. v26, 1967, for Continuous Tube Finned Heat Exchanger.

SUMMARY OF THE INVENTION A stack of fins and end elements have apertures aligned forming a plurality of through openings. The stack is placed in a tray which is periodically advanced to align the openings seriatim along the center of the machine along which the tube is pushed and pulled through the openings to form loops on the ends. Similar devices are employed in opposite ends of the machine to push and pull the tube through the openings on the center of the devices. The pulling device is moved a substantial distance because of the substantial length of the tube which is drawn through the first opening.

A reversing device is provided between the pulling device and the fins which is moved outwardly relative to the pulling device and spaced a predetermined distance therefrom so that a predetermined length of tube can be reversed. The reversal device is then in position to grasp the tube as it is released from the pulling device and bend the tube about a mandrel and form a large loop when reversing the end length. The length is located on the machine center line so that when a stack of fins is indexed to locate the next adjacent opening on the center line, the return movement of the pulling device picks up the reversing device and advances the tube toward and through the opening a sutficient distance to have the free end in position to be engaged by the pulling device on the opposite side of the fin stack. The tube has a wire extending therethrough with the ball or other expanding element on the remote end so that after the tube has been inserted through the first opening, the wire can be pulled to draw the ball through the length of tube withint he opening to expand the wall into heat contacting relation with the fins and a predetermined distance therebeyond substantially that required to form the loop. The wire is then cut off with a short portion extending from the tube so that it will advance ahead of the tube through an opening each time the tube is threaded therethrough. Each time a loop is formed the wire is pulled to expand the wall of the tube within the opening and a portion therebeyond. Thereafter a section of wire is cut off to have the necessary length extending beyond the tube end in position to be gripped and pulled after the tube is inserted through the next adjacent opening and a loop is formed. With this arrangement the threading and expanding operations occur alternately so that when the last straight portion has had the ball or expanding element drawn therethrough, the heat exchanger is completed.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a broken plan view of a machine which practices the method of the present invention;

FIG. 2 is a side view of the machine illustrated in FIG. 1;

FIG. 3 is a sectional view of the structure illustrated in FIG. 2, taken on the line 3-3 thereof;

FIG. 4 is a broken side view of the structure illustrated in FIG. 3;

FIG. 5 is an enlarged broken sectional view of the structure illustrated in FIG. 2, taken on the line 5-5 thereof;

FIG. 6 is a reduced broken view of a structure illus-v trated in FIG. 5, showing a loop being formed;

FIG. 7 is a view of the structure illustrated in FIG. 6 after the loop has been completed;

FIG. 8 is a large broken view of the structure illustrated in FIG. 1, showing the end of the tube reversed;

FIG. 9 is an enlarged sectional view of the structure illustrated in FIG. 3, taken on the line 99 thereof;

FIG. 10 is a sectional view of the structure illustrated in FIG. 9, taken on the line 1010 thereof;

FIG. 11 is a view in elevation of a sensing device useable on the machine illustrated in FIG. 5;

FIG. 12 is a sectional view of a ball attached to a wire for expanding the tube;

FIG. 13 is a sectional end view of the structure illustrated in FIG. 12, taken on the line 1313 thereof, and

FIG. 14 is a sectional view of a wire with two expanding elements thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT The method and the machine for practicing the present invention is illustrated in the drawings. The machine has central uprights 11 and 12 and supporting posts 13 at the ends. The posts and uprights support a pair of guide rods 14 on which pulling devices 15 and 18 and reversing devices 16 and 17 are slidably mounted on opposite sides of the uprights 11 and 12 respectively. The pulling devices 15 and 18 are mounted on upright channels 19 which are supporter on carriages 21 and 22 having wheels 23 thereon which run upon a pair of tracks '24. A pair of cylinders 25 and 26 are sup-. ported between the tracks having a piston rod 27 and 28 extending therefrom and connected to plates 29 and 31 which are attached to the carriages 21 and 22 re? spectively. v

The uprights 11 and 12 support a platform 32 on which a slide 3 3 is mounted for incremental movement. A tray 34 rests upon the slide 33 and abuts a pair of stop elements 35 on the slide. A stack of 'fins 36 with end chan nels 37 are mounted in the tray and accurately spaced from each other by collars 38 about the apertures. The

apertures are aligned forming a plurality of openings 39 through the stack which extends above the end flanges 41 of the slide 33.

The tray has a bar on the bottom which mates with a slot 43 in the platform 32. The bar has downward extending teeth which are engaged by a pawl carried by a head on a piston rod within a cylinder 48 which is attached to the bottom of the platform 32. The pulling devices and 18 have a clamping jaw 49 each of which is actuated by a cylinder 51 to open and closed positions. When the jaws are in open position the end of the tube may be swung away therefrom in a horizontal plane. The jaws 49 on the pulling devices 15 and -18 are in aligned relation on the center of the machine which is indicated by a line '52 having arrows at each end.

The reversing devices 16 and 17, as illustrated in FIGS. 1 and 2, have a head 53 mounted on the rods 14. The head 53 has a rotatable jaw 54 containing clamping elements for grasping the tube. The jaw 54 is rotatably supported on a raising and lowering device described in detail in the first above mentioned application. The jaw has a gear sector which is rotated by a rack operated by a ram 56. After a tube 59 has been drawn through an opening in the stack of fins and end elements, the jaw 54 is raised to have the tube clamped by the clamping elements thereof. Thereafter the rack is operated by the ram 56 to rotate the jaw and tube 180. The head 53 has a pair of rods 61 slidably extending therethrough with a nut 60 on the forward end, the opposite end being fixed to the pulling devices 15 and -18. A ram 62 is mounted on a plate 63 supported in cantilever on a pair of uprights 58. The ram supports a semicircular element 64 and a similar ram and element is inverted and supported therebelow so that the two half elements can be moved into abutted engagement. The two half elements have arcuate recesses about which the tube 59 is drawn when forming a loop 65 at the ends of the heat exchange unit. By moving two semicircular elements 64 together, the loop can be formed in the arcuate groove after which the two halves are separated to permit the loop 65 formed thereby to be indexed therebeyond. As disclosed in the above applications, after the, tube 59 had been threaded through all of the openings 38 of the assembled fins 36 and end elements 37, the tube was expanded into good conductive relationship with the fins.

' The expansion of the tube as practiced by the present method is done in steps during the threading operation by pulling a ball through the straight portion of the tube within an opening and a distance therebeyond. When the tube 59 is prepared for insertion in the first of the openings 38 in the fins and end element, a wire 66 is run therethrough having a ball 67 on the remote end. The ball is forced into the tube a short distance, suificient to have a desired length extending beyond the adjacent end element. This locates the ball within the tube adjacent to the end element in which position it is desirable to have the ball at the beginning of a pulling operation. The wire extends outwardly of the end of the tube and moves with the tube when the tube is grasped by the jaw 49 and pulled. After being passed through an opening 39 in the fin stack the tube end will strike a plate 68 after the wire 66 has'been guided by a tapered aperture 69 into pulling jaws 71. The cylinder 51 will be actuated to close the jaw 49 onto the end of the tube '59 and fluid will be delivered to cylinder 26 to move the carriage 21 to the left, as viewed in FIG. 1. At the end of the stroke the ball 67 will be located adjacent to the end element 37 and the fluid to the cylinder 26 is cut off. Fluid is then admitted to a cylinder 72 to clamp the jaws 71 on the end of the wire 66. Thereupon, a cylinder 73 carried on the head 15 by a" plate 74 will advance a plate 75 to which the jaws 71 are secured to pull the wire the length of the cylinder. This advances the ball through the straight portion of the tube which is within the opening 39 to expand the walls against the collars 38 of the fins and the edge of the aperture of the end elements 37. The ball is moved therebeyond an amount substantially equal to the length of the loop, as illustrated in FIGS. 5 and 6 so that after the loop is formed the ball 67 will be at the end thereof adjacent the next straight portion in position to be advanced therethrough.

In FIG. 8, the predetermined lentgh of tube 59 has been reversed with the wire 66 extending therefrom ready to be advanced into the next opening 39 after the slide 33 has been indexed to place the opening in alignment with the end of the tube and wire. As pointed out in the above copending applications, the carriage 21 will be advanced toward the slide to advance the reversing head 16 and the reversed length of tube through the opening 39.to a position where the jaw 49 on the opposite side of the machine is in position to clamp the end of the tube and pull it through the opening and form the loop thereon. The extending end of the wire will be clamped by the jaws 71 so that it may be pulled to advance the ball through the straight portions and into the length of tubing which will form the next loop.

As-illustrated in FIG. 9, a cutter head 76 is advanced by springs 77 against a stop 78 after the cylinder 73 has advanced the wire its full length at which time a cutter blade 79 is actuated by a ram 81 to cut off the wire maintaining a desired length in extension of the end of the tube 59. The head 76 will be retracted against the pressure of the spring 77 by the plate 75 when returned by the cylinder to have the jaws'71 disposed in position to grasp the end of the protruding wire 66.

A plate 68 actuates a valve 82 to operate the cylinder 51 to close the jaw 49. The plate 68 has a slot 83 therein which is aligned with the wire 66 and with a slot 84 in the cutter head 76. When the jaws are opened the end of the wire 66 can move through the slots 83 and '84 in a horizontal path when the tube is being rotated 180", as illustrated in FIG. 8, as explained more fully in the above mentioned applications.

The ball 67, as illustrated in FIGS. 12 and 13, preferably has an aperture 85 therethrough twice the diameter of the wire 66. This permits the wire to be folded and inserted through the ball with a free end 86 and an extending end 87 bent at right angles over the ball so that the wire can not move back and forth relative to the ball. This is desirable to prevent the wire after being cut from moving backward because of the tension therein so that the wire end will extend its same distance beyond the ball and the same length of pull will occur and the ball will be accurately located each operation. Since any such error would be cumulative, the ball would be located further and further away from the position at the end of a loop. It is within the purview of the invention to employ two balls 88 and 8 9, as illustrated in FIG. 14, on the wire which are slightly different in diameters so that the expansions will occur at spaced points which will require substantially less force than that required when one ball produced the expansion. By using the two balls the size of the wire can be reduced.

If difiiculty is experienced due to the accumulation of errors in positioning the ball 67 in the tube, various types of locating devices can be provided for producing an indication that the ball has reached the desired point. One such device is illustrated in FIG. 11, wherein a U-shaped magnetic core 91 has a central section removed to provide a space slightly greater than the diameter of the tube 59. Coils 92 and 93 are disposed on the arms of the core to produce a field therein. An armature 94 is pivoted to one end of the core 91, the opposite end being biased from the other end of the core by a plunger 95 of a switch 96. The magnification produced in the core by the coils 92 and 93 is not suflicient to draw the armature 94 thereagainst and the switch 95 will not be actuated until the ball passes through the space 90 whereupon the strength of the field in the core 91 will move the armature 94 downwardly to move the plunger 95 into the switch 96 and complete a circuit therethrough. This circuit will operate a solenoid valve to stop the movement of the ram 93 and in this manner the ball is accurately positioned in the tube each operation, as clearly illustrated in FIG. 5. The core 91 is carried on a frame 97 which is suspended upon a piston rod 98 of a ram 99 which raises and lowers the core when the tube is being manipulated. Just prior to the time that the wire is to be pulled, the ram 99 will lower the core to the position illustrated in FIGS. 5 and 11 so that the armature 94 will be'actuated when the ball reaches the space 90 in the core 91.

It will be noted in FIGS. 5 and 6 that the end of the tube 59 which is advanced has a length of a sleeve 100 therein to strengthen the tube end and prevent it from being distorted when repeatedly clamped in the jaws 49. The sleeve is also useful for centering the wire 66 in the end to prevent it from drooping and engage the collars 38 of the fins 36 and cause damage thereto. A conical element can be employed for guiding the tube end when it is inserted in an opening 39 as disclosed in the above applications.

The present disclosure clearly illustrates how the wire is placed within the tube with a ball on the remote end. After the tube is moved through the first opening 39 the wire is pulled to expand the tube wall against the collars 38 of the fins 36 and end elements 37 in fixed heat conductive relationship therewith. The pull is of a length not only to pass the ball through the straight portion but also through the straight portion of the tube which will form the next loop. The tube and wire is threaded back and forth through the series of openings 39 in the stack of fins and end plate, as illustrated and described in the above mentioned copending application. After each loop is formed the ball is pulled through the straight portion to produce the expansion thereof and the length to form the loop. When the ball is pulled from the last straight portion of the tube, the heat exchanger is completed having all the parts in fixed conductive relation to each other and no further work is required on the assembly of the various elements of the heat exchanger.

When the tube is made of materials which are difiicult to braze, a length of copper tubing may be applied to the projecting ends, as mentioned in the above described copending application. With this arrangement the brazing of the ends into a heat exchanger system can be done by brazing copper to copper. While the operation of the machine requires a considerable number of sequential steps, the pilot systems for operating solenoids, valves and other elementshas not been shown and described in detail as it is within the purview of anyone skilled in the art to locate such elements required in the system at the points at which they are to be operated. By employing the machine to practice the method, a complete heat exchanger is constructed in a single cycle of machine operation. All of the parts of the heat exchanger will be in firm fixed conductive relation to each other without any possibility of the presence of open joints which could cause leaks.

What is claimed is:

1. The method of constructing a heat exchanger which includes the steps of: threading a continuous length of tube back and forth through a stack of fins which have a plurality of openings therein, and pulling an expanding element through the continuous length of tube in steps after each straight portion is established within an openmg.

2. The method as recited in claim 1, wherein the expanding element is pulled a distance to be located within a loop next to be formed on the side adjacent to the'next straight portion to be located in an opening.

3. The method as recited in claim 1, wherein the expanding element is pulled by a wire a length of which is cut off after each pulling thereof which is substantially equal in length to the distance the wire was pulled.

4. The method as recited in claim 3, wherein the distance the wire is pulled is controlled by the distance the pulling device is advanced.

5. The method as recited in claim 3, wherein the distance the wire is pulled is controlled by a sensing device which interrupts the pulling operation when actuated by the presence of the expanding element.

6. The method as recited in claim 4, wherein the end of the tube being pulled is reinforced on the inside in a manner to center the wire extending therefrom.

7. The method of constructing a heat exchanger which includes the steps of: forming a stack of a plurality of fins having a plurality of aligned apertures therethrough forming openings, passing a length of tube through a first opening, pulling a wire within the tube to advance an expanding element through the portion of the tube within the opening, cutting oil the extending length of wire which is substantially equal to the distance the Wire was pulled, reversing the end of the tube with the short length of wire extending therefrom and advancing the tube and wire through an adjacent opening to form another straight portion with a loop therebetween, pulling the Wire to advance the expanding element through the straight portion just formed and a portion of the length of tube which will form the next loop and continuing the step of forming straight portions and loops and expanding the straight portions until the heat exchanger is completed with all parts in firm, heat conducting relationship.

8. In a machine for constructing a heat exchanger, an indexible tray for advancing a stack of fins having spaced openings therein for locating one of said openings at a tube receiving station, means at each side of the machine for pulling a continuous length of tube through the opening located at the station each time the tray is indexed and form a loop at the edge of the stack first from one side of the machine and then from the other side thereof, and means for expanding the length of tube within the opening each time a loop is formed.

9 In a machine for constructing a heat exchanger as recited in claim 8, wherein said expanding means is a wire extending through the tube with an expanding element on the end, and means for clamping the projecting end of the wire and pulling a predetermined length thereof from the tube end.

10. In a machine for constructing a heat exchanger as recited in claim 9, wherein means are provided for cutting 011 a length of the pulled wire which is substantially equal to the length of wire pulled.

11. In a machine for constructing a heat exchanger as recited in claim 10, wherein a sleeve is secured in the end of the tube which is pulled to strengthen the wall thereof and to center the Wire extending therefrom.

References Cited UNITED STATES PATENTS 1,646,384 10/ 1927 Bergstrom 29-157.3 2,023,738 12/1935 Mason et a1.

2,064,036 12/ 1936 Sandberg 1131 18 2,494,548 1/ 1950 Goldberg 151 X 2,948,054 8/ 1960 Kritzer 29-157.3 2,994,123 8/1961 Kritzer 29-1573 JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner US. Cl. X.R. 2933, 202, 433 

